Pipe welding fixtures or mounts used to secure a length of pipe so that the pipe may be manipulated during welding are well known. Particularly in welding, it is desirable for a welder to have the capability to apply a weld so that the welder's torch is placed on top of the joint to be welded, and then to rotate the workpiece around the position of the torch. If a welder is required to physically move the torch around the curved surface of the pipe, this greatly increases the difficulty for the welder to produce a consistent bead. Additionally, requiring the torch to be moved also greatly increases the time in which it takes to produce the weld, and raises safety concerns when a welder's helper or apprentice must hold the section of pipe being welded.
One common device used to rotate a workpiece during welding is a spinner tool that secures the workpiece, and enables the welder to rotate the workpiece by use of a wheel or handle that spins the workpiece about an axis of rotation. However, a welder must often join various sections of pipe wherein one section has an offset created by a 90° bend in the section of pipe. Since such a pipe section is not centered about the axis of rotation, the spinner tool is difficult to manipulate because the section of pipe is imbalanced.
One reference that addresses this weight imbalance problem is the U.S. Pat. No. 5,265,789 directed to a pipe welding counterweight support apparatus. The apparatus includes a support pipe having a counterweight slidably mounted therealong. The support pipe has a v-shaped lock that receives the pipe to be welded. A clamp chain is used to secure the pipe to the v-shaped lock.
Another reference that provides a solution for an imbalanced pipe section to be welded is found in U.S. Pat. No. 4,058,025. This reference discloses a counterweight assembly including a weight carriage having a frame that attaches to the pipe, and an adjusting assembly allowing the counterweight assembly to vary the amount of counterweight to be provided.
Although the prior art may be adequate for its intended purposes, one disadvantage suffered by the prior art is that many counterweight devices are structurally complex, and are difficult to install on the pipe to be welded. Additionally, the prior art suffers in that the counterweight devices are not adapted for use with a common spinner tool.
Therefore, it is one object of the present invention to provide an improved counterweight assembly that is simple in construction, yet provides a welder with an effective means to selectively vary a counterweight used to balance a workpiece so that it may be rotated in a safe and efficient manner.
It is another object of the invention to provide a counterweight assembly that may be used in combination with a spinner tool that is mounted to a portable vise found at the work site, thereby eliminating the need to mount the spinner tool and counterweight assembly to a worktable or other support remote from the work site.